Milia form when tiny flakes of a protein called keratin get trapped beneath the surface of your skin instead of shedding naturally. Keratin is the same tough protein that makes up your hair and the outermost layer of your skin. When it becomes enclosed in a small pocket just under the surface, it creates a firm, pearly-white bump typically 1 to 2 millimeters across. The process behind that trapping varies depending on the type of milia and what triggered it.
How Primary Milia Develop
Primary milia are the most common type and appear without any obvious injury or skin condition. They develop from the lining of tiny vellus hair follicles, the nearly invisible fine hairs that cover most of your face. Specifically, they originate from the lower portion of the hair follicle near where oil glands attach. Histological studies show strand-like connections running from the milium cyst directly to the outer root sheath of the vellus hair, confirming that the follicle itself is the starting point.
In simple terms, the hair follicle’s lining produces keratin cells that normally migrate upward and flake off. When that process stalls or the opening gets blocked, keratin accumulates and forms a tiny enclosed cyst. Because nothing is inflamed or infected, the bump sits quietly under the skin, white or yellowish, and feels like a small, hard seed when you run your finger over it.
Primary milia show up most often on the eyelids, forehead, and cheeks. They affect people of all ages, and up to 50 percent of newborns develop them. In babies, these spots typically disappear on their own within the first one to three months of life as the skin matures and begins turning over cells more efficiently. In adults, primary milia tend to be more stubborn and can persist for months or even years.
Why Secondary Milia Are Different
Secondary milia form after something damages the skin. Burns, blistering rashes, dermabrasion, and significant sunburns can all trigger them. They can also appear as a reaction to heavy skin creams or ointments. While primary milia originate from hair follicles, secondary milia most often develop from sweat ducts. Research examining tissue samples found that 75 percent of secondary milia connected directly to a sweat duct, usually at the base of the cyst, in a one-to-one ratio.
The mechanism is straightforward: when skin is injured, the normal architecture of hair follicles, sweat ducts, and surface layers gets disrupted during healing. As new tissue forms, keratin can become walled off in small pockets rather than reaching the surface. This is why secondary milia tend to cluster in the exact area where the injury occurred, unlike primary milia, which can appear seemingly at random across the face.
Sun Damage and Skin Thickening
Chronic UV exposure is one of the most significant external contributors to milia in adults. Years of sun exposure thickens the outermost layer of skin and damages the proteins responsible for maintaining elasticity. When the epidermis becomes leathery and rigid, it doesn’t shed dead cells as efficiently. Keratin gets trapped more easily beneath a surface that has essentially become too tough and inflexible to let it pass through normally.
This explains why milia become increasingly common with age, particularly in people who have spent years outdoors without consistent sun protection. The combination of naturally slowing cell turnover and cumulative UV damage creates ideal conditions for keratin to accumulate in small cysts rather than cycling off the skin’s surface.
Skincare Products That Contribute
Certain skincare ingredients can physically seal the skin’s surface, trapping dead cells underneath. Petrolatum, mineral oil, lanolin, and thick synthetic waxes are the most common culprits. These heavy occlusives form a barrier that prevents the normal shedding of keratin flakes, especially around the delicate skin near the eyes where milia frequently appear.
Heavy botanical oils applied thickly overnight can also contribute, and rich overnight balms are particularly problematic in the eye area. If you notice milia developing after starting a new product, switching to a lighter, non-comedogenic moisturizer often helps prevent new ones from forming. The milia that are already there, however, won’t resolve just from changing products, since the keratin is already sealed inside its cyst.
How Milia Differ From Similar Bumps
Milia are sometimes confused with closed comedones (whiteheads) or syringomas. Closed comedones contain a plug of oil and dead skin cells inside a pore and can be extracted with gentle pressure. Milia have no pore opening at all, which is why squeezing them does nothing.
Syringomas are small sweat gland growths that also cluster around the eyes, but they look different up close. They tend to be yellow or skin-toned rather than pearly white, and they’re firm bumps typically 1 to 3 millimeters across. Unlike milia, syringomas are actual tissue growths rather than keratin-filled cysts, so they require different treatment.
How Milia Are Removed
In newborns, no treatment is needed. The bumps resolve as the skin matures. In adults, milia rarely go away on their own because the cyst wall keeps the keratin sealed inside with no exit route.
The standard removal technique involves a dermatologist using a fine sterile needle (often an insulin syringe needle) to puncture the thin layer of skin covering the cyst, then gently extracting the keratin plug. Some practitioners use the syringe’s suction to draw out the contents without damaging surrounding tissue. Larger milia that have migrated closer to the surface can sometimes be removed simply with gauze pressure after the initial puncture.
For prevention or to address widespread milia, topical retinoids are commonly recommended. These vitamin A derivatives speed up cell turnover, encouraging keratin to shed from the surface normally rather than becoming trapped. Retinol (the milder over-the-counter form) or prescription-strength retinoids are applied once daily to clean, dry skin. Consistent use over several weeks helps thin the outer skin layer enough that existing milia may resolve and new ones are less likely to form.
Combining a retinoid with gentle chemical exfoliation and switching away from heavy occlusive products addresses the three most controllable factors: slow cell turnover, surface buildup, and pore-sealing ingredients. Sun protection rounds out the strategy by preventing the UV-driven skin thickening that makes milia increasingly common over time.